This invention relates to a welding apparatus and particularly to a continuous electrical welding apparatus having a high welding current efficiency.
Heretofore, welding rods have been commonly employed for welding purposes. In the welding operation, a welding rod consisting of a relatively short rod about 30 centimeters in length is used. The rod has a welding flux material coated on its surface. Such a welding rod provides a good quality weld in application and it only requires a rather simple welding equipment to carry out the welding operation. However, due to the relatively short length of such welding rod, in most welding operations, it is necessary to use a plurality of such rod to accomplish the task. Therefore, the weld formed in the welding operation by using a plurality of welding rods would have a plurality of weld sections therein formed by the use of the separate welding rods. The plurality of weld sections are thus not integrally formed and would inherently have many joints between adjacent sections. Such separately formed weld sections do not have a strong bond with each other, and they have a rough surface appearance whereas if the weld is continuously formed, there would be no joints in the weld and its would have a smooth surface.
Furthermore, in using a Welding rod, the welding current is necessarily supplied through the entire length of the welding rod to the work piece. Due to the inherent internal resistance in the metal core of the welding rod, a large amount of current is lost in flowing through the rod, so that the efficiency of the welding current is low.
Attempts have been made to provide an elongated welding electrode such that the welding operation can be accomplished with a single length of electrode continuously without having to disrupt the welding operation to provide new electrodes. In such continuous welding electrode, the welding metal is in the form of an elongated metal tube having welding flux material contained within the tube. However, such elongated tubular welding-electrode is extremely complex and expensive to produce mainly due to the difficulty in placing the welding flux material inside the metal tube. Moreover, since the welding current is still subject to loss when passing through such elongated welding electrode, the efficiency of the welding current is low and the weld formed with such electrode is low in quality.
In pending U.S. patent application Ser. No. 08/195,443 filed in Feb. 7, 1994 by the present Applicant, it is shown a high efficiency welding device which has a drive mechanism for feeding a continuous welding electrode to a weld area as well as simultaneously applying the high welding current in multiple contact points close to the front end of the electrode to eliminate the problem of current loss through welding electrode as in the use of welding rods. The drive mechanism shown therein consists mainly of a pair of drive chains driven directly by two pairs of driving gears. Although the device shown therein is satisfactory in providing a high current continuous welding operation, it is complex in structure and the welding electrode can only be fed to the work area in a constant single speed.